1. Field of the Invention
This invention relates to a solid electrolyte. More particularly, it relates to a lithium-ionic-conductive solid electrolyte which has a high lithium ionic conductivity even at the normal temperature and which produces especially favorable results when used in a lithium cell, an electrochromic display, etc.
2. Description of the Prior Art
As is well known, electrochemical devices which employ solid electrolytes having the lithium ionic conductance have many merits such as being free from the fear of leakage and providing a long lifetime, and permitting an extraordinarily small and thin structure. Therefore, many uses such as very thin batteries and electrochromic displays are expected of them. Since, however, prior-art solid electrolytes are very low in the lithium ionic conductivity at the normal temperature, they are not extensively employed at present.
Regarding the solid electrolytes exhibiting the lithium ionic conductance, there have been proposed, for example, a lithium cell which employs LiNaO.9Al.sub.2 O.sub.3 as a solid electrolyte (Japanese Published Unexamined patent application No. 52-103635) and a solid electrolyte consisting of a sulfate of pyridine and Li.sub.2 SO.sub.4 (Japanese Published Unexamined patent application No. 53-115694). All such solid electrolytes, however, have the disadvantage as above stated that the lithium ionic conductance is not very great.
Unless the lithium ionic conductance is great, there is, for example, the problem that a high current density is not attained when the solid electrolyte is applied to a lithium cell. Therefore, the lithium-ionic-conductive solid electrolyte needs to have as high a lithium ionic conductivity as possible.